Show Hints / Candidates will help you see the available pencil values within the cell, row, column, and boxes.

Sudoku How To Technique: Naked Pair

This Sudoku solving method starts the concept of “it has to be one of these two, therefore it can’t be anywhere else within that block”. CELLS R6C1 and R6C3 only have two possible valid HINTS within their shared BLOCK (ROW R6 and BOX 3). Since we know that CELLS R6C1 can either be a value of {3,5} and R6C3 can either be a value of {3,5}, that other CELLS within their shared BLOCKS (R6 and BOX 3) cannot by logic have a valid HINT of {3 or 5}. Therefore, it is safe to remove the HINT value of {3} from R6C7, R6C8, and R6C9.

If you look closer at the shared BOX 4, the cells the CELLS R5C3 and R4C4 have HINTS {3,5}. Keeping with the same logic before, it would be safe to remove those HINTS from those cells.